The invention relates to a device for fixed-rolling radii or recesses on main and connecting rod bearings of crankshafts by means of fixed rollers and supporting rollers on the respective main or connecting rod bearings to support the rolling force exerted on the crankshaft by the fixed rollers.
Fixed-rolling crankshafts using an additional external force applied in the direction of the load arising during operation is known in the art. For example, when fixed-rolling crankshafts consisting of high-strength materials, the rolling forces can be so great that the crankshafts can no longer be fixed-rolled with the normal tools without the fixed-rollers failing after a short time. The load of a tensile stress during fixed-rolling would allow the external load to reduce the rolling force to generate a similar distribution of axial internal stresses as during fixed-rolling without an external load. In crankshafts, this external load during fixed-rolling corresponds to an elastic bending of the crankshaft bearers (compare Achmus, Christian: xe2x80x9cMeasurement and Calculation of the Edge Layer State of Complex Components after Fixed Rollingxe2x80x9d, authorized dissertation, Braunschweig Technical University, 1998, Papierflieger publishing house, Clausthal-Zellerfeld, 1999, pp. 110 and 111).
The results of the aforementioned publication give rise to the object of this invention, which is to further develop known devices for fixed-rolling radii or recesses on main or connecting rod bearings of crankshafts in such a way as to impart a higher service life to conventional fixed-rolling tools, or fixed-roll crankshafts consisting of a high-strength material using conventional fixed-rolling tools with the usual service life. In this case, the further developed devices must be simple in design, safe to use and inexpensive.
The object is achieved by a device for applying an additional external stress in the direction of the load on the crankshaft that arises during operation while fixed-rolling the radii or recesses. In a preferred embodiment, the device consists of at least one clamping chuck for the crankshaft, which can exert a tensile force on the crankshaft in the longitudinal direction of the crankshaft.
However, the object of the invention can also be solved by applying a bending moment on the crankshaft. Such an arrangement can then consist of a clamping chuck, a tailstock or a collar plate, between which the crankshaft is clamped. The clamping chuck, tailstock or collar plate are designed in such a way that they can generate a bending stress in the crankshaft while the crankshaft rotates during the fixed-rolling process. A bending stress can be generated, for example, by setting the aforementioned elements at an angle or laterally shifting in a radial direction of the crankshaft.
One particularly simple design for the device is obtained by drawing upon the supporting rollers used for supporting the fixed rollers to apply an additional bending force. In addition, the bearers of the crankshaft can also be expanded with the help of additional expanding rollers.